add is_multioutput method to DummyModel in tests

Author: radka-j

tests/experimental/test_experimental_base.py

@@ -119,6 +119,10 @@ def get_tune_config():
                 "batch_size": [16],
             }
 
+        @staticmethod
+        def is_multioutput():
+            return False
+
     def setup_method(self):
         """
         Define the PyTorchBackend instance.

tests/experimental/test_experimental_model_selection.py

@@ -25,6 +25,10 @@ def predict(self, x):
         def get_tune_config():
             return {}
 
+        @staticmethod
+        def is_multioutput():
+            return False
+
     x = torch.tensor(np.arange(32)).float()
     y = 2 * x
     dataset = TensorDataset(x, y)